Low-temperature reduction of cobalt chloride



Patented June 16, 1953 LOW-TEMPERATURE REDUCTION COBALT CHLORIDE Edward A. Beidler, Columbus, Ohio, assignor, by

mesne assignments, to Crowley-Republic Steel Cleveland, Ohio, a corporation of Corporation,

Delaware No Drawing. Application May 23, 1950,

Serial No. 163,792

The present invention relates to the low-tem perature reduction of cobalt chloride and more particularly to the reduction of cobalt chloride to form finely divided metallic cobalt at temperatures below that at which this material could be reduced in the absence of a catalyst in ac cordance with previously known methods.

For many purposes it is desiredto prepare cobalt in a very finely divided condition; Such material may, for example, find use as an alloying agent in various metallurgical practices.

Finely divided cobalt is useful in powder metallurgy, particularly where the cobalt is'to be I mixed with some other powdered metal,- for example iron, in making composite articles. When the cobalt used is in a veryfinely divided condition, the resulting articles made by powder metallurgy processes are much more hcmegeneous than if the cobalt were used in the form of coarser particles. fineness of the cobalt powder may make for greater strength in a product made therefrom.

It. is known that cobalt powder formed by chemically reducing a compound of cobalt is smaller in particle size substantially in propor- 1 tion as the temperature at which the reduction takes place is lower. For this reason, it has been desired, when finely divided cobalt is the desired product, to effect the reduction at as low a tern perature or temperature range as possible. Prior art practices and certain tests hereinafter set out in the examples given demonstrate that at temperatures below about 690% F. the reduction to cobalt from one of its salts, for example, from cobalt chloride, proceeds at such an extremely slow rate that it may be said for practical purposes that it is impossible to reduce cobalt chloride below this temperature in the absence of some catalyst which will enable the reaction to take place at an appreciable rate in the desired lower temperature range.

The present invention may be summarized In some instances also the 4 Claims. I (Cl.*750.5) v

'the presence of at least a trace or a so-called threshold amount of the catalyst.

It is further found that the rate of such reduction is enhanced by greater amounts of the catalyst and also, independently, by increased temperatures in the range at which the reduction reaction takes place. It has been found, forexample, that at temperatures above about 690 F. the reaction will go' on even without a catalyst toinitiate it, even though the reduced material at these higher temperatures is in much larger particle size than is desired in accordance with the present invention.

While'it is contemplated, and it has -been' proven as hereinafter set forth, that a trace or a so-called threshold amount-only of the catalyst (i. e., finely divided -metallic cobalt) will be sufficient to initiate 'the reduction 'r'eaction, it is believed that, from a practical standpoint,

at least about 0.1% of metallic cobalt (calcu-' lated by'weightbasedupon the weight of the cobalt chloride to be reduced) is required in order to start the reduction reaction at any appreciable and economical practicable rate. For this reason the minimum amount of metallic cobalt normally usable in initiating the reduction of the cobalt chloride may be said for purposes of this invention to be about 0.1 calculated as aforesaid. V I

In view of the fact that larger amounts of the catalyst will cause the reaction to occur with greater rapidity even ata given temperature, it

is useful to employ larger amounts of the catalystthan the minimum above referred to. This causes no substantial loss, as the product itself all) therefore as one providing a process for the preparation of finely divided metallic cobalt from a salt of cobalt, for example, cobalt chloride, in a temperature range of about 510 F. to about 690 F.- Inthis range it is found that the reduction reaction will take place if it is catalyzed by the presence in the mass to be reduced of-a desired catalyst, namely, finely divided metallic cobalt, the product of the reduction reaction. Inasmuch as the catalyst is itself the product of the reaction being catalyzed, it may be said that the process is autocatalytic, that is, it will proceed at a practical rate once it is initiated by is the catalyst and, therefore, a portion thereof may be returned from one "batch to a succeeding batch in the practical working of the process. In this way the only-loss in the re peated practice of the process is the heat that isrequired to re-heat a certain amount of the catalyst, i. e, the product of an earlier batch. Corresponding economies may be effected on a continuousbasis of operation. Thefprocess as a whole, which is carried on at a substantially lower temperature than was heretofore deemed possible, will save a much larger total amount a of heat than that lost as aforesaid and hence is more economical.

The process of the present invention is best illustrated by the following examples:

Example I Hydrated cobalt chloride (C'oCl2.2H2O) was first dehydrated in a stream of nitrogen at about 700 F., then cooled to about 675 F. and the nitrogen atmosphere exchanged ,for a hydrogen atmosphere which was caused to how continuously past the sample for about 6 hours. Careful check was made of the outgoing or exhaust gas to determine the presence of any HCl therein which would result from reduction of the material of the sample by the hydrogen. There was no reduction perceptible by this test in the time permitted as aforesaid. When, however, without other change, the temperature was raised to the range of about 690 F. to about 725 K, perceptible reduction started as was evidenced by the presence of H01 in the exit gas.

Example II p at the reducing conditions stated in Example I' in th hydrogen atmosphere. The results were identical with those given in Example I.

Example III A sample of anhydrous cobalt chloride to which about 16% of its weight of finely divided metallic cobalt was added and thoroughly admixed was exposed as in Examples I and II to a flow of hydrogen, first at about 500 F. At this temperature, there was no discernible reduction taking place as evidenced by the fact that no HCl was found in the exit gas. Upon the tem,- perature being raised to aboutv 510 F. the exit gases began to show some I-ICl content. As the temperature was progressively raised in about steps, the HCl content in the gases was progressively greater, indicating a progressively increased rate of reduction as the temperature was raised.

Example IV I The same test as in Example III was made, using cobalt chloride dihydrate in lieu of anhydrous cobalt chloride. The results were exactly the same as in Example III above.

It has been found that in order to reduce cobalt chloride to metallic cobalt, the gaseous reducing agent must contain hydrogen, as hydrogen is the only gas which has been found, in accordance with the present invention, to be effective in reducing cobalt to metallic cobalt chloride. It seems immaterial what the proportion of the hydrogen is in the gases or what other gases may be present, assuming, that is, that the other gase are not positively oxidizing or chloridizing in character. These other gases are preferably substantially neutral in character, such as nitrogen, for example. For this reason hydrogen. is considered, in accordance with the present invention, to be the essential active reducing ingredient of the gas to which the cobalt chloride is exposed in order to effect the reduction thereof.

From the above it will be noted that one way of practicing the process of the present invention is to mix with cobalt chloride, with or without I water of crystallization, a desired amount of. finely divided metallic cobalt as a catalyst to Z initiate the reducing reaction in the low! tern-v peratur range. Another way of attaining the same results is, of course, in any way to provide in the mass of cobalt chloride to be reduced, the

desired catalyst. As it has been found, as above set forth, that the reduction will take place in the absence of a catalyst at higher temperatures, this high temperature reduction may sometimes be resorted to to form or to establish in the mass, the desired amount of metallic cobalt to act as the catalyst. Following the establishment of the initial desired amount, the temperature may be lowered to a point or range within the desired range in accordance with the present invention, i. e., from about 510 F. to about 690 F., and then the process of the present invention carried on. The present process is to be considered to include such practice.

While there is herein described but one principal process and certain variants thereof, the present invention is intended to include all reasonable equivalents of the step specifically set out herein, as will occur to those skilled in the art from theforegoing disclosure.

What is claimed is:

1. The process of initiating the reduction of solid cobalt chloride (C0012) with hydrogen by a dry gas-to-solid reaction to form metallic cobalt in a temperature range in which hydrogen and COClz will not commence to react together to any substantial extent in the absence of a reaction-initiating catalyst, comprising the steps of contacting dry solid C0C12, which is substantially free of metallic cobalt, with a gas containing hydrogen as its essential active reducing ingredient, while maintaining. said CoClz in the temperature range of about 510 F. to about 690 F., and causing the reaction to start by providing in contact with the C0C12 at least about 0.1% (by weight based upon the COClz) of metallic cobalt as a reaction-initiating catalyst.

2. The process according to claim 1, wherein said gas consists of hydrogen.

3. The process according to claim 1, wherein there is provided in contact with said cobalt chloride about 16% of finely divided metallic cobalt for initiating th reduction of said cobalt chloride.

4. The process according to claim 1, in which said metallic cobalt for use as a reaction-initiating catalyst is provided by forming such metallic cobalt in situ by reducing some C0C12 at a temperature above 690 F.

EDWARD A. BEIDLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,373,654 Danckwardt Apr. 5, 1921 1,522,813 Etchells Jan. 13, 1925 1,783,662 Marx et a1. Dec. 2, 1930 OTHER REFERENCES Societe Chimique De France, Bulletin; vol. 35, 1924. Article by M. G. Crut. Pages 550-584, inclusive, and 729-741, inclusive.

Comprehensive Treatise On Inorganic and Theoretical Chemistry, by Mellor, vol. 14, 1935, page 451 and vol. 15, l936,-pages 3 and 411. Published by Longmans, Green & Co., London, England. 

1. THE PROCESS OF INITIATING THE REDUCTION OF SOLID COBALT CHLORIDE (COCL2) WITH HYDROGEN BY A DRY GAS-TO-SOLID REACTION TO FORM METALLIC COBALT IN A TEMPERATURE RANGE IN WHICH HYDROGEN AND COCL2 WILL NOT COMMENCE TO REACT TOGETHER TO ANY SUBSTANTIAL EXTENT IN THE ABSENCE OF A REACTION-INITATING CATALYST, COMPRISING THE STEPS OF CONTACTING DRY SOLID COCL2, WHICH IS SUBSTANTIALLY FREE OF METALLIC COBALT, WITH A GAS CONTAINING HYDROGEN AS ITS ESSENTIAL ACTIVE REDUCING INGREDIENT, WHILE MAINTAINING SAID COC62 IN THE TEMPERATUE RANGE OF ABOUT 510* F. TO ABOUT 690* F., AND CAUSING THE REACTION TO START BY PROVIDING IN CONTACT WITH THE COCL2 AT LEAST ABOUT 0.1% (BY WEIGHT BASED UPON THE COCL2) OF METALLIC COBALT AS A REACTION-INITIATING CATALYST. 